DATA SHEET
command definitions). In addition, the following hard-
ware data protection measures prevent accidental
erasure or programming, which might otherwise be
caused by spurious system level signals during V
CC
power-up and power-down transitions, or from system
noise.
Low V
CC
Write Inhibit
Perform Erase or
Program Operations
START
RESET# = V
ID
(Note 1)
RESET# = V
IH
Temporary Sector
Unprotect Completed
(Note 2)
When V
CC
is less than V
LKO
, the device does not
accept any write cycles. This protects data during V
CC
power-up and power-down. The command register and
all internal program/erase circuits are disabled, and the
device resets. Subsequent writes are ignored until V
CC
is greater than V
LKO
. The system must provide the
proper signals to the control pins to prevent uninten-
tional writes when V
CC
is greater than V
LKO
.
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE#, CE# or
WE# do not initiate a write cycle.
Logical Inhibit
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once
again.
Write cycles are inhibited by holding any one of OE# =
V
IL
, CE# = V
IH
or WE# = V
IH
. To initiate a write cycle,
CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = V
IL
and OE# = V
IH
during power up, the
device does not accept commands on the rising edge
of WE#. The internal state machine is automatically
reset to reading array data on power-up.
Figure 2.
Temporary Sector Unprotect Operation
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadver tent writes (refer to Table 5 for
COMMAND DEFINITIONS
Writing specific address and data commands or
sequences into the command register initiates device
operations. Table 5 defines the valid register command
sequences. Writing
incorrect address and data
values
or writing them in the
improper sequence
resets the device to reading array data.
All addresses are latched on the falling edge of WE# or
CE#, whichever happens later. All data is latched on
the rising edge of WE# or CE#, whichever happens
first. Refer to the appropriate timing diagrams in the
After the device accepts an Erase Suspend command,
the device enters the Erase Suspend mode. The
system can read array data using the standard read
timings, except that if it reads at an address within
erase-suspended sectors, the device outputs status
data. After completing a programming operation in the
Erase Suspend mode, the system may once again
read array data with the same exception. See “Erase
mation on this mode.
The system
must
issue the reset command to re-
enable the device for reading array data if DQ5 goes
high, or while in the autoselect mode. See the “Reset
See also “Requirements for Reading Array Data” in the
The Read Operations table provides the read parame-
ters, and Figure 13 shows the timing diagram.
Reading Array Data
The device is automatically set to reading array data
after device power-up. No commands are required to
retrieve data. The device is also ready to read array
data after completing an Embedded Program or
Embedded Erase algorithm.
14
Am29LV004B
21522D5 October 11, 2006
AMD [ ADVANCED MICRO DEVICES ]
